In a prior art construction of drafting frames for spinning machines and the like, the support and loading arms for the upper rollers of the drafting units are mounted on holding bars which are connected to the bridge plates which are individual to that drafting unit. One of the problems with such a design is that the stability of the machine is limited and, indeed, the stiffness of the drafting frame and the stiffness of the entire machine frame leaves much to be desired, especially when the distances between the intermediate stands is large. In fact, as a practical matter, in such systems the spacing between the intermediate stands cannot be increased over about 1200 mm without creating problems.
In British Patent Document GB 2 233 354, a system is described in which the holding bars for the swingable pressing arms of the drafting units span between the intermediate stands, i.e. run from one intermediate stand to another.
Here, however, no bridge pieces or plates are provided and again there is a limit to the spacing between the intermediate stands which is significantly less than is desirable and even smaller than other conventional designs.
A drafting frame system for spinning machines is described in German Patent Document DE-OS 24 22 422 in which the supporting parts of the drafting units are so formed that a large number of drafting units can be mounted. The longitudinal supporting member in this case includes a holding bar which is at least twice as long as the distance between two stamped pieces. The holding bars extend through intermediate stands in which the stamped pieces and the supporting and loading arms of the drafting units are held. In this case, the holding bars are not supported by the stamped pieces but rather the stamped pieces must be held by the holding bars. The resulting drafting frame or the machine frame in the mounted state of the drafting frame generally cannot be reinforced as to stiffness and often is insufficiently stiff to satisfy modern requirements as to the lengths of the textile machine.
In another arrangement of drafting units on a spinning machine (see German Patent Document DE-OS 26 56 537) premounted drafting units are provided as well.
In one embodiment, the stamped pieces are connected by a longitudinal profiled element in the form of an auxiliary drafting rail. The holding bars extend only from stamped piece to stamped piece and the unit extends as disclosed only along one side of the machine.
German Patent Document DE-GM 1 971 929 describes a so-called bridge plate, also produced by stamping, which extends to both sides of the machine of a two-sided ring spinning machine and which is supported by girder means in the form of a pair of tubular girders constituting the supporting member.